Added support for --verbose and --quiet
Moved ArgOptions instantiating to text UI context
Fixed typo
Improved flag argument support

Added support for --flag arguments without the need of consecutive
boolean argument, i.e. the user can run:

    ./hippo --strict src/

instead of having to do

    ./hippo --strict 1 src/

or

    ./hippo --strict -- src/
Inlined arg option consts
Added argument array type hinting

This is continuation from previous commits, where we introduced flag
type hinting to deal with "--flag not_a_bool" problem.